In an information recording medium, such as a CD and a DVD, for example, as described in patent documents 1 and 2 or the like, there is also developed an information recording medium, such as a multilayer type or dual layer type optical disc, in which a plurality of recording layers are provided on the same substrate. Then, on an information recording apparatus, such as a DVD recorder, for performing the recording with respect to the dual layer type, i.e., two-layer type, optical disc, laser light for recording is focused or condensed on a recording layer located on the front as viewed from the irradiation side of the laser light (hereinafter referred to as an “L0 layer”, as occasion demands), to thereby record information into the L0 layer in an irreversible change recording method by heat or a rewritable method. Moreover, the laser light is focused or condensed on a recording layer located on the rear of the L0 layer as viewed from the irradiation side of the laser light (hereinafter referred to as an “L1 layer”, as occasion demands), through the L0 layer or the like, to thereby record information into the L1 layer in the irreversible change recording method by heat or the rewritable method.
Moreover, there is also disclosed a technology of performing the recording in a DAO recording method with respect to the L0 layer and the L1 layer. Here, the DAO (Disk At Once) method is a method in which a controlling device, such as a CPU (Central Processing Unit), on a disc drive side or a host computer side, for example, gains an understanding of the entire amount of information to be recorded, before an actual recording operation, and the information to be recorded (defined as “record information” in this application) is continuously recorded onto the information recording medium from a lead-in area to a lead-out area by one recording operation. In particular, it is possible to realize the maintenance of compatibility with a DVD-VIDEO/ROM.
On the other hand, there is also disclosed a technology of performing the recording or reproduction in an “opposite method” or a “parallel method” with respect to the L0 layer and the L1 layer. The “opposite method” herein is a recording or reproduction method in which the directions of track paths are opposite between the two recording layers, for example. As opposed to this, the “parallel method” is a recording or reproduction method in which the directions of track paths are the same between the two recording layers, for example.
Incidentally, in the “opposite method”, if the recording or reproduction is ended in the L0 layer, an optical pickup, located on the most outer circumference of the optical disc, does not have to be displaced to the most inner circumference again when the recording or reproduction is started in the L1 layer, and it is only necessary to change the focal distance from the L0 layer to the L1 layer. Thus, there is an advantage that a changing time from the L0 layer to the L1 layer is shorter than that in the parallel method. This is why the opposite method is adopted in the recording of large volumes of content information which requires continuous reproduction.    Patent document 1: Japanese Patent Application Laid Open NO. 2000-311346    Patent document 2: Japanese Patent Application Laid Open NO. 2001-23237    Patent document 3: Japanese Patent Application Laid Open NO. Hei 9-231613    Patent document 1: Japanese Patent Application Laid Open NO. 2002-358660    Patent document 5: Japanese Patent Application Laid Open NO. 2001-126255